Evaluation of sunlight stability of polyurethane elastomers for maxillofacial use. I

Abstract

The evaluation of the efficiency of polymer additives with special emphasis on uv absorbers and antioxidants in polyurethane elastomers has been completed. Aliphatic polyurethanes were chosen for this study because their properties closely relate to the requirements of maxillofacial prosthesis. The polyurethane elastomers were either synthesized by ourselves or formulated according to the manufacturer's recommendation. Eleven different types of uv absorbes, coupled with one antioxidant, were incorporated into the polyurethane systems. The Atlas twin-lamp carbon arc Weatherometer was used as the source of uv. The samples were periodically withdrawn for examination of yellowing and tackiness. It was found that, although the incorporation of uv stabilizers enhanced the uv resistance of polyurethanes, the problem of tackiness resulting from uv aging was not solved satisfactorily. The phenomenon of yellowing, however, was significantly improved, mainly due to the aliphatic structure of polyurethanes. The most promising uv absorbers are Tinuvin 770 and the combination of Tinuvin 328, ZnO, and an antioxidant. Their effectiveness in other polyurethane systems is not known and further research is underway to explore this field. Hopefully, these findings will greatly assist the successful application polyurethane elastomers in maxillofacial prosthesis.

Evaluation of the effect of ultraviolet stabilizers on the change in color of pigmented silicone elastomer: An in vitro study

“…[81415161718] UV stabilizers have been used extensively in the polymer, paint, cosmetic, and plastic industries as well as for wood and cellulose fabrics to prevent color degradation and increase the life of the products. [192021]…”

“…Chu and Fischer[17] used 1.5% weight UVA and found that it was effective in reducing yellowing of the elastomer, Lemon et al . [8] used 12%, 25% by weight UVA and found that these did not protect the samples and Tran et al .…”

“…The addition of UV stabilizers, thermochromic pigments, and opacifiers to improve the color stability of pigmented elastomers have been tried in the past with varied results. [1415161718]…”

Evaluation of the effect of ultraviolet stabilizers on the change in color of a silicone elastomer following aging by three different methods:An in vitro study

“…[7][8][9][10]24 The strategies for stabilization of elastomers have included the use of UV stabilizers, thermochromic pigments and opacifiers. 7,[13][14][15][16][17] Such attempts at stabilization of elastomers have yielded mixed results. Kantola 14 found that thermochromic pigments were very sensitive to UV radiation and not suitable for prosthetic application whereas Kiat-amnuay 13 studied various concentrations of opacifiers and found that they prevent colour degradation overtime.…”

“…In the past, varying concentrations of UV stabilizers have been documented by researchers with mixed results (Chu and Fischer et al 16 used 1.5% weight UVA and found that it was effective in reducing yellowing of the elastomer, Lemon et al 7 used 12%, .25% by weight UVA and found that these did not protect the samples and Tran et al 15 used 75% by weight UVA and HALS and found that this was effective only for a certain pigmented groups). In this study 1% by weight of UVA (Chimassorb 81) and 1% by weight of HALS (Uvinul 5050) for Groups B and C respectively and 0.5% of each for Group D was used.…”